I needed a hook for my wire shelf in my workshop to hang things that just don't do well in containers so I designed this. For standard wire shelving, use 7 mm as the inner diameter and 20 or 21 for a maximum width for the hook. The rest is up to you has to what you want to do.

This was my first try at writing a parametric design in openSCAD. Please feel free to comment on the design. I plan on making a change with version 2 which will allow the choice of rectangular or circular bottom hook.